Why is Gul'dan considered the most powerful mortal Warlock in existence?

It is said Gul'dan was a mortal Warlock who's power stretched beyond the extent of any mortal Necromancer/Warlock in existence, but he did not even attempt to battle or kill Doomhammer, a completely normal warrior, in the numerous times Doomhammer cornered him. Eventually, he was slain almost effortlessly by lower class demons suspected to be Naga.

Just because a spellcaster is an almost god-like force, doesn't mean a gold ol' ax to the head wouldn't kill him. Also, even if he could easily kill doomhammer, orcs would have turned against him. A solitary warlock, no matter how potent, could not take on all that wrath himself.

Gul'dan helped, but it wasn't just that. The manipulation and complete control of the orcs, the corruption of a ton of races, acts of sheer power over nature like raising the hand of Gul'dan in SMV, creating the first death knights, reading Medivh's mind from across the planet, the list of his unique accomplishments is pretty long.

And if you don't want to speculate based on his achievements, suffice to say his skull is one of the most powerful artifacts and therefore his person must have been one of the most powerful as well.

Gul'dan helped, but it wasn't just that. The manipulation and complete control of the orcs, the corruption of a ton of races, acts of sheer power over nature like raising the hand of Gul'dan in SMV, creating the first death knights, reading Medivh's mind from across the planet, the list of his unique accomplishments is pretty long.

And if you don't want to speculate based on his achievements, suffice to say his skull is one of the most powerful artifacts and therefore his person must have been one of the most powerful as well.

Well, he was chosen by Kil'Jaeden himself to form the bloodthirsty Orcish horde when Outland was still Draenor, in exchange for great powers. He then severed the ties between the Orcs of Draenor and the elemental spirits, while he also raised a huge volcane in the center of Shadowmoon Valley.
He then oversaw the slaughter and almost total annihilation of the Draenei who resided in Draenor as well as helping Medivh opening the Dark Portal which in turn led to the invasion.

Finally, he raised the islands on where the Tomb of Sargaras was located.

He did all of these things, and countless many more just to sate his thirst for power. I'd say that makes him pretty evil, also considering the fact that his skull was turned into an artifact which turned Felwood into what it is today AND turned Illidan Stromrage into a half demon.

Originally Posted by Salandrin

All this and he didn't just vaporize Doomhammer and some Naga?

Considering he was entering a tomb filled with demons who probably were a manifest of the powers of Sargaras, I'd say his death was quite.. Epic. I don't know where people get the idea that the Naga would be inside a sealed tomb

Gul'dan severed the connection of the elements from Draenor. Ner'zhul shattered it with his portals and dragged it into the twisting nether. But ya stuff never adds up. Gul'dan is powerful enough to make death knights, command mighty demons and sever the elements from a planet and gets felled by lesser demons/possibly naga and has to resort to subversion to spy on his enemies and assassinate them rather than flay their souls outright. Sylvanas is the fearless leader of the Forsaken and taken down by a shotgun blast to the face. Tyrande is supposed to be a powerful priestess whom can heal/shield herself, fire magically guided arrows and resurrect the fallen, yet she's taken out of battle by a single arrow in Woflheart. Azshara is the most powerful sorceress in existence and can't even figure out how to cast unending breath on herself and her raid group to stop them from drowning... etc etc.

It is said Gul'dan was a mortal Warlock who's power stretched beyond the extent of any mortal Necromancer/Warlock in existence, but he did not even attempt to battle or kill Doomhammer, a completely normal warrior, in the numerous times Doomhammer cornered him. Eventually, he was slain almost effortlessly by lower class demons suspected to be Naga.

I just don't understand.

Maybe raising the Tomb of Sargeras and breaking the seals on it drained him.

he screwed up the most stuff, currupted the most stuff and it took the Tomb of Sargaras to bring him down WITH effort and he still got his back by graffiti-ing up their entire place with his blood, ruining the property values for Eons.

Well, he was chosen by Kil'Jaeden himself to form the bloodthirsty Orcish horde when Outland was still Draenor, in exchange for great powers. He then severed the ties between the Orcs of Draenor and the elemental spirits, while he also raised a huge volcane in the center of Shadowmoon Valley.
He then oversaw the slaughter and almost total annihilation of the Draenei who resided in Draenor as well as helping Medivh opening the Dark Portal which in turn led to the invasion.

Finally, he raised the islands on where the Tomb of Sargaras was located.

He did all of these things, and countless many more just to sate his thirst for power. I'd say that makes him pretty evil, also considering the fact that his skull was turned into an artifact which turned Felwood into what it is today AND turned Illidan Stromrage into a half demon.

Your timeline is off. Ner'zhul was contacted by Kil'jaeden (in disguise) and lead the assault on the Draenei. When the spirits abandoned the Orcs, Ner'zhul went to Oshu'gun to investigate. There, the real spirit revealed Kil'jaeden's deception. Ner'zhul confronted Kil'jaeden and was struck down. He was succeeded by his apprentice, Gul'dan. Gul'dan then made the pact with Kil'jaeden and Mannoroth to enslave the Orcs. The Orcs in their demonic bloodlust ravaged the planet and began fighting amongst themselves until Medivh contacted Gul'dan. Gul'dan then unified the clans for the invasion of Azeroth.

Originally Posted by Blizzard Entertainment

´So.. sorry to bring this up but..you know that .."thing" (Med'an).. is that "thing" cannon still?
...as much have some have wished otherwise, yes. (Loreology)

Maybe raising the Tomb of Sargeras and breaking the seals on it drained him.

Or he was sick that day.

Or some stuff in WoW is just really inconsistent.

Or he didn't consider there would be an actual demonic army in there. I mean, he got very far, very far indeed. He almost found the Eye of Sargeras in fact, but eventually he was left alone when all his warlocks got slaughtered.

As for why he didn't challenge Doomhammer directly, many of the clan chieftains disliked, mistrusted or downright hated him, yet they supported Doomhammer. Gul'dan was nothing if not cunning.

Considering he was entering a tomb filled with demons who probably were a manifest of the powers of Sargaras, I'd say his death was quite.. Epic. I don't know where people get the idea that the Naga would be inside a sealed tomb

However, there is also possibility that fiends that Gul'dan encountered in the tomb were Naga. Several pieces of evidence support this theory. At the end of seventeenth chapter in "Tides of Darkness", a novel by Aaron Rosenberg, there is short description of those fiends as they emerged from the building and attacked orc forces that were sent by Doomhammer to kill Gul'dan for his betrayal. It describes how one creature had too many limbs and too many joints and altogether too many teeth; and that it was soon followed by others. In first part of twelfth chapter in "Beyond the Dark Portal", a novel by Aaron Rosenberg & Christie Golden; death knight Ragnok Bloodreaver, Tagar Spinebreaker, chieftain of the Bonechewer clan, Fenris Wolfbrother, chieftain of the Thunderlord clan, and other orcs from both clans joined together in swift assault on the Tomb of Sargeras to claim Jeweled Scepter of Sargeras. There they encountered the fiend that was holding the very scepter. "Creature was so tall that it was forced to hunch within the room beyond. Its skin was scaled and covered in bumps that seemed to ripple, as if somehow its surface were fluid like water. Spikes jutted form the shoulders, the forearms, the chest, and various other places, The over-long arms ended in huge hands with long claws. The face was too narrow at the bottom and too wide at the top, with slanting eyes that glowed a smoky, roiling yellow and a tiny mouth somehow filled with a insane number of razor-sharp teeth. A long tail whipped about behind it." The description has very strong similarities with Naga's appearance. Furthermore, the location and history of the location of the tomb potentially link it to the Naga. During the Sundering, several ancient Kaldorei capitals were destroyed and Queen Azshara was forced to make pact with the Old Gods in order to save herself and her people from drowning. And so the Old Gods used their dark powers on drowning Highborne and transformed her and the Highborne into Naga. These vengeful humanoid sea serpents were filled with hate and rage, their monstrous appearance reflecting the wickedness and malice that had always hidden within their core. Since then Naga have occupied most of the sunken parts of their old kingdom and because of this, it is highly possible that they also inhabited the very tomb as well, as it is part of their former capital Suramar.

That's a rather silly theory, I'd say. The entity in the BtDP novel seems to have had legs for one, plus there were masses of demons inside the tomb in TFT. It's possible it was a further, demonically-powered mutation of a naga, though. Then again, it could also have simply been a type of demon we haven't encountered yet.

I think that because among other things, at one point he kind of rocked up to Shadowmoon Valley, waggled his fingers and went "Blergh. Mountain."

Plus, you know... The whole being a catalyst for his world's destruction and his races corruption with fel energy, creating legions of necromantic orc spirits locked in the bodies of human knights, the whole opening of portals to other dimensions allowing his entire race to invade, you know... the small stuff.